Fuel and fuel cooler with lamellar inner structures for connecting to the air-conditioning system

ABSTRACT

A fuel cooling apparatus for a motor vehicle includes an outer housing having connections for a supply pipe and a discharge pipe with the supply pipe and the discharge pipe being integrated into opposite walls of the outer housing in a diagonally mismatched position. There is a conduit pipe inside the outer housing connecting the supply pipe to the discharge pipe in a direction of flow with the conduit pipe being widened for forming a cell having lamellas oriented parallel to the direction of flow. The cell having the lamellas preferably includes cross-linkages for forming a network structure for mixing fluids flowing through the lamellas for supporting heat exchange.

The invention relates to a vehicle with combustion engine, fuel tank andair condition and a heat exchanger connected with the fuel pipe that isintegrated into the coolant circulation system of the air condition. Thefuel cooling unit consists of an outer housing with connection forfeeder and discharge pipes and a pipe running inside the outer housing.

Fuel may heat upon in a vehicle for various reasons. The fuel in thetank may heat up due to the heat produced by solar radiation or the fuelin the fuel pipes may heat up due to the radiation heat coming fromdrive sites and the radiation heat produced in the exhaust gas facility.The heated up fuel, steam bubble may develop in the fuel which interruptthe smooth operation of the engine. The technical term used for theselittle interruptions is “misfire”. This problem particularly occurs whendriving at high speeds and in case of compressor and turbo engines witha high consumption. That is why engineers have been making effort todevelop devices for cooling the fuel for long time. This is reflected bythe large number of patents and disclosure documents describing fuelcooling units.

When taking a closer look at these documents that deal with the interiordesign of the fuel cooling unit it becomes apparent that these devicesgenerally refer to improvement inventions aimed at increasing thecooling effect which is mainly determined by the size of the heattransmission surface and the distribution of the coolant. That is whydesign modification efforts have been made in order to enlarge this heattransmission surface to enhance distribution of coolant in the majorityof devices designed as fluid-heat exchangers. The efforts made toimprove the coolant distribution aim at flushing the fuel-carrying pipeswith coolant homogenously. The following is a short description of thedocuments to be regarded among state-of-the-art papers.

The device described in DE 34 40 060 refers to a fuel cooling unit wherethe fuel to be cooled is pumped through a curled hose which has theshape of a coil. This curled hose is radially supported by the innerwall of the radiator housing, while the cylindrical housing is flushedwith coolant in axial direction. Due to restricted space available andbending problems, the coil has been made in 5 different individualpieces for this device. This device shows to major disadvantages: lowcooling performance and the difficult manufacturing process of the coil.

Document DE 41 10 264 A1 outlines a recommendation for improvement ofthe cooling performance of the device described in DE 34 40 060 A1: Inorder to avoid the effect that the cooling performance stays constantdespite higher coolant throughput or may even be reduced, the corecross-section of the fuel-carrying coil was filled with a body on whichthe fluid is flowing. This flow body was designed as twist sheet in thiscase which can be inserted between two adjoining windings of the curledhose coil. The contours of this twist sheet redefine the flowingcross-section going through the coil inside the housing and lead to amore homogenous flushing of the fuel-carrying coil.

Document DE 37 40 811 A1 recommends a spherical surface type housinginstead of the cylindrical basic shape of the fuel cooling unit used sofar which is fitted with a spiral with the fuel to be cooled in aposition that allows the windings of the spiral to be positioneddiagonally to the coolant stream. This subjects the stream of thecoolant to new thermal start-up procedures at each winding which leadsto turbulent currents which ensure good flushing of the fuel-carryingpipes.

Document DE 44 37 167 A1 describes a fuel cooling unit which shows amuch larger heat transmission surface. Cylindrical bellows are used inthis device as the major component of the fuel cooling unit between theends of a fuel-feeding and a fuel-discharging pipe. The fuel coolingunit is equipped with a housing that consists of a hollow cylindersection with fuel feeding and fuel-discharging pipe and a lateral edge.ring-waved bellows are positioned inside the housing cover in a radialdistance which is fixed on a hollow cylindrical guidance body of thesame length with no play.

The guidance body is equipped with a wall in the current cross-sectionthat is inclined towards the current direction which ranges over theentire length of the guidance body which is connected in one piece withits front and rear end as related to the current direction of thecoolant with the adjoining end of the guidance body. Openings arelocated at both sides of the wall in the hollow cylindrical cover of theguidance body which are positioned in diametrically opposed to eachother. The openings positioned in parallel along the axle of the coverline of the guidance body terminate on the outside of the guidance bodyin the flanks of the all-round bellows curves open towards the insidewhile fuel is being transported in the flanks of the bellows curves opentowards the outside in the opposite direction. The fuel is permanentlyforced alongside the bellows curves open towards the inside through thewall positioned in an inclined position towards the current direction ofthe fuel so that on such enlarged heat transmission surface there can bean optimal heat exchange with the fuel streaming on the other side ofthe flanks.

The complicated technical design and the necessity for exact fixation ofthe guidance element which is a material precondition for a correct feedof fuel or coolant to the individual bellows curves are disadvantages ofthis device. Furthermore, no large throughput rates are possible due tothe small cross-section of the bellows curves

Connection of a fuel cooling unit to the coolant circulation system ofthe air condition is already state-of-the-art: Document DE 37 25 664 A1describes the installation of a fuel cooling unit not further describedregarding its inner design into the coolant circulation before theevaporator, while document DE 33 30 250 A provides for the installationof a fuel cooling unit not further described in more detail, either,between evaporator and compressor.

The invention is associated with the problem of designing a fuel coolingunit to be installed into vehicles with air condition which offers aheat exchange surface of sufficient size in case of a simple design inorder to ensure homogenous distribution of the coolant so that a highfuel throughput rate can be guaranteed at high speeds.

In order to solve this task, the invention describes a fuel cooling unitwhere

the pipe (3) located inside the outer housing is widened to a cell andwhere

the cell created by widening the pipe (3) is equipped with lamellas (5)at the inside in parallel position to the current direction.

The core piece of the invention is based on the idea that a contactsurface for heat exchange between fuel and coolant is created where theareas next to the contact surface are designed to guarantee quicker heatexchange. That is why two housings were fit into one another andadditionally, a network structure was integrated in the interior of theinner housing consisting of lamellas with cross-links. The cross-linksbetween the lamellas positioned in current direction provide for a quickheat exchange between the individual lamellas at the one hand and ensurea homogenous mix of the coolant in the relevant clearance spaces. Thisconstant mixing of the coolant is another important precondition for aquick heat exchange.

The advantages of the fuel cooling unit as outlined in this inventionare numerous. Cooling of the fuel prevents the development of steambubbles and evaporation of fuel additives. This supports optimalcombustion of the fuel with minimum emission. This results in a smoothidle operation and, in particular, improved performance of engines withhigher fuel consumption. Higher engine performance and better fueleconomy could be proved by measurements. Furthermore, the heat exchangeras outlined in the invention supports trouble-free new start of engineswhich are warm from operation. Due to the fact that cooled fuel can becompressed more easily, the strongest effect of the fuel cooling unit asoutlined in the invention is achieved for compressor and turbo engines.The lamella-type structures inside the fuel cooling unit accelerate heattransportation to both sides of the heat transmission surface andstabilise the outer housing and the inner cells whenever higherpressures occur.

There are two designs available for the fuel cooling unit as outlined inthe invention. The outer housing may be integrated into the fuel pipebetween fuel tank and fuel pump or into the coolant circulation systemof the air condition. If the first option is chosen, i.e. installationin the outer housing of the fuel pipe the inner cell will be integratedinto the coolant circulation system of the air condition. In case thesecond design is preferred, it might be possible to integrate the innercell into the fuel pipe and to connect the outer housing to the coolantcirculation system of the air condition. (The first preferred option wasused for test measurements performed so far, i.e. the outer housing wasintegrated into the fuel pipe between fuel tank and fuel pump, while theinner cell was connected to the coolant circulation system of the aircondition.)

Based on another invention feature, the fuel cooling unit can also beintegrated into the coolant circulation system before or after theevaporator of the air condition.

If the fuel cooling unit is integrated into the coolant circulationsystem after the evaporator, this will result in a relatively limitedcooling of the fuel. However, cooling performance will be higher, if thefuel cooling unit is integrated into the cooling circulation systembefore the evaporator.

The invention further provides that the current direction of the fuelinside the fuel cooling unit is moving in the opposite direction of thecurrent direction of the coolant. The opposite current direction of fueland coolant will beneficially result in an improved cooling performance.

Another material feature of the invention is that the sections notfilled by the inner cell inside the outer housing are also equipped withlamellas which are positioned in parallel towards the current directionand which in a specially preferred design are linked to a networkstructure like the lamellas inside the inner cell by additionalcross-links. The network structure in both hollow bodies provides for anacceleration of the heat transport to the lamellas located further awayfrom the border surface and results in a swirling of the fluids furtheroptimizing heat transport and to a homogenous flushing of the bordersurface towards both sides.

Another particularly preferred design of the fuel cooling unit outlinedin the invention provides that the outer housing and the cell in theinterior consist of six side surfaces in vertical position to each othereach. The middle lines of the rectangular parallelepiped hollow bodiesmeet in the assembled fuel cooling unit. In this case the inner cell isshorter in longitudinal direction than the outer cell so that thereremains a clearance between the two hollow bodies which is filled byfuel and coolant in the operating condition.

Another preferred design of the fuel cooling unit outlined in theinvention provides that the outer height of the rectangularparallelepiped cell corresponds exactly with the inner height of theouter housing so that the inner cell is optimally fitted with its topand bottom side without any clearance in the outer housing. Since thetwo pipe connections of the outer housing are integrated into eachrespective wall of the top and bottom side of the housing in adiagonally mismatched position, the inner cell is flushed by fuel or bycoolant at least two long sides and at the two front sides in theoperating condition in this preferred design.

It corresponds to the idea of the invention that the components used todesign the outer housing and the inner cell and the lamellas and thecross-links inside both hollow bodies are made of a metal with highthermal conductivity such as aluminium or copper. When using aluminium,tungsten inert gas welding (wig welding) with a needle is used toconnect the components. This way the connections, which have differentsizes because of the various throughput levels, and the fine-steelcoated fuel hoses which also may have different diameters, can be fixed.The different connection sizes are adapted to each vehicle and enginevariant helping to achieve the best possible engine performance.

For further details and features of the invention, please refer to thefollowing descriptive part of the drawing. The drawing and thepertaining description are not designed to limit the invention, butshould render further detailed information.

FIG. 1 shows one of several possible designs of the fuel cooling unit asoutlined in the invention. Inner cell 3 is positioned inside outerhousing 1. Connections 4 a and 4 b belonging to inner cell leave housing1 on the front sides. Lamellas 5 positioned in current direction andcross-links not completely illustrated can be seen inside the innercell. The cross-links provide for a mixing of the fluids when flowingthrough the lamellas thereby supporting heat exchange.

The connections of the outer housing 2 a and 2 b are located indiagonally mismatched position on the two side surfaces of outer housing1. The space not filled by inner cell 3 inside outer housing 1 is notfilled with lamellas and respective cross-links in the exampleillustrated here. Of course, another design could be possible where thisclearance is filled with lamellas and cross-links like shown for innercell 3.

1-16. (canceled)
 17. A fuel cooling apparatus for a motor vehicle,comprising: an outer housing having means for connecting a supply pipeand a discharge pipe with said supply pipe and said discharge pipe beingintegrated into opposite walls of said outer housing in a diagonallymismatched position; and, a conduit pipe inside said outer housing andconnecting from the supply pipe to the discharge pipe in a direction offlow, said conduit pipe being widened for forming a cell having lamellasoriented parallel to the direction of flow.
 18. The fuel coolingapparatus for a motor vehicle according to claim 17, wherein said cellhaving said lamellas includes cross-linkages for forming a networkstructure for mixing fluids flowing through said lamellas for supportingheat exchange.
 19. The fuel cooling apparatus for a motor vehicleaccording to claim 17, wherein said outer housing and said cell insidesaid outer housing have six-sided surfaces vertically positionedrelative to one another.
 20. The fuel cooling apparatus for a motorvehicle according to claim 17, wherein said cell has a rectangularparallelepiped structure.
 21. The fuel cooling apparatus for a motorvehicle according to claim 17, further comprising a supply connectionand a discharge connection for said cell within said outer housing, saidsupply connection and said discharge connection being integrated intoopposite walls of said outer housing in a diagonally mismatchedposition.
 22. The fuel cooling apparatus for a motor vehicle accordingto claim 17, wherein said outer housing is made of a metal having a highthermal conductivity.
 23. The fuel cooling apparatus for a motor vehicleaccording to claim 17, wherein said cell is made of a metal having ahigh thermal conductivity.
 24. The fuel cooling apparatus for a motorvehicle according to claim 17, wherein said lamellas of said cell aremade of a metal having a high thermal conductivity.